diff --git a/ldapalchemy/dbutils.py b/ldapalchemy/dbutils.py
index 009cd7956bc93d7da39a6d93bc7b4b466455a24d..f7b0f098981358b8a6f60ab9d3d62938956543c7 100644
--- a/ldapalchemy/dbutils.py
+++ b/ldapalchemy/dbutils.py
@@ -59,7 +59,10 @@ class DBRelationship:
 			return self
 		if self.mapcls is not None:
 			return DBRelationshipSet(obj, self.relattr, self.ldapcls, self.mapcls)
-		return self.ldapcls.query.get(getattr(obj, self.relattr))
+		dn = getattr(obj, self.relattr)
+		if dn is not None:
+			return self.ldapcls.query.get(dn)
+		return None
 
 	def __set__(self, obj, values):
 		if self.mapcls is not None: